1. Field of the Invention
The present invention relates generally to scuba diving first stage pressure regulators. The invention relates more specifically to a silicone or rubber-like material bonded onto a first stage regulator intermediate pressure spring for the purpose of providing freeze protection and to a method of molding silicone or rubber-line material to a compressed first stage spring to eliminate any induced stress added by the material. The use of a flexible membrane or diaphragm used in eliminating water and contamination from entering the ambient pressure cavity where the spring is housed is also described.
2. Background Art
Scuba diving first stage regulators need freeze protection if used in waters lower than 50 degrees Fahrenheit (10 degrees Celsius).
Flow through piston regulators can freeze “open” when used in cold water conditions if not fitted with proper antifreeze or environmental provisions. When this “open” circuit failing occurs, high-pressure air from the tank travels directly to the second stage without the required low-pressure reduction to 135 PSI. The second stage is now overcome by high-pressure air and free-flows violently and uncontrollably through the diver's mouthpiece.
Just prior to a freeze-related first stage failure, the diver is breathing normally from the second stage. Then a slight free flow of air develops and begins to exit the second stage. This constant flow of air cools the first stage more than normal breathing rates with intermittent cycles. Suddenly, and without warning the flow of air from the mouthpiece is an uncontrolled free flow of air, the diver begins losing his air supply and must immediately ascend to the surface. This is a very traumatic event for the diver.
This freeze up is caused by the following: As high pressure air is reduced to low pressure air inside the first stage regulator, the pressure drop results in breathing air expanding rapidly. As it expands, it cools to sub zero temperatures instantly. This cooling effect is known as the adiabatic process.
Because first stage components are constructed mainly of metals such as brass, stainless steel, or titanium, internal cold air temperatures are conducted away from the critical first stage internal components and into the surrounding water through these metal structures. In some cases, if the surrounding water temperature is below 50 degrees Fahrenheit or (10 degrees Celsius), ice will begin to form on and around critical first stage metal components, specifically inside and between the first stage intermediate pressure spring coils located inside the ambient pressure sending cavity area. Once ice begins to form, the effectiveness of cold thermal transfer is highly diminished.
The first stage regulator spring cavity or ambient chamber is especially prone to freezing water that enters the first stage for the purpose of regulating intermediate pressure over hydrostatic pressure. Just seconds before freezing, the final amount of clearance between the spring coils is displaced by ice and the intermediate pressure spring becomes locked or frozen solid. Because it is now blocked and cannot deflect or close, the first stage starts to fail in the open flow position due to limited piston and spring movement. Restricted forward piston movement results in the open flow path of high-pressure air between the seat and piston, not permitting the shut off position between the piston and the high-pressure seat.
Compressed air exits the scuba diver's air cylinder and tank valve and flows into the first stage regulator as it is reduced from a high “3500 PSI” supply pressure to a low 135 PSI intermediate pressure as it exits the first stage. This intermediate pressure is always regulated to be over hydrostatic pressure or 135 PSI plus the ambient water pressure of 0.445 PSI per foot depth of seawater.
A flow through piston end moves away from a high-pressure seat far enough to allow for the flow of air to occur. As air travels through a hollow stem of the piston to the opposite large diameter side of the piston, it builds in pressure. Pressure is allowed to build behind the larger pressure sending side of the piston while being resisted by a predetermined amount of spring force applied from an intermediate pressure spring. This force is calculated to maintain the desired intermediate pressure of 135 PSI. Once the desired intermediate pressure is reached, the spring force is overcome and the piston travels to close off the piston and high-pressure seat air passage into the hollow piston stem. Airflow is thereby halted for the time being.
The reason the intermediate pressure chamber is open to water contact and how it regulates “over-bottom pressure” may be described as follows: The flow through piston and intermediate pressure spring must work together in order to sense and regulate intermediate pressure to 135 PSI over ambient water pressure or over-bottom pressure at all depths to which the diver descends or ascends. To accomplish this, the piston and spring design must add or subtract 0.445 PSI for each foot depth of seawater to maintain the 135 PSI over ambient hydrostatic pressure.
If the intermediate pressure chamber is sealed dry and no pressure transmitting forces can register on the piston, the first stage intermediate pressure cannot correct to surrounding hydrostatic pressure, thus flow and output are diminished.
One method used to prevent water from freezing inside the ambient chamber is to keep the chamber dry. This is very logical but very difficult to accomplish. One design creates a very small hole through the piston head to allow intermediate pressure to communicate into the ambient pressure chamber while still keeping it dry. Inside the chamber, a small pressure over the surrounding water pressure is allowed to build and overcome a rubber check valve where air exits the first stage. The stream of small bubbles exiting the check valve appears to other divers as an o-ring leak. This method of keeping the chamber dry is a marketing challenge for the maker.
The prior art attempts to thermally isolate the cold transfer by blocking the path of cold air flowing through the piston stem. Unfortunately, under freezing conditions, the spring coils will form with ice and fail due to this blockage. Water must be prevented from entering the ambient pressure chamber and freezing between the coils of the intermediate pressure spring to eliminate the potential for freezing. Prior art attempts to thermally isolate cold from the intermediate pressure spring does not address the issue of water entering the intermediate pressure cavity and freezing between the spring coils. Such attempts only prolong the time required to freeze the water.
If water is allowed to enter the regulator first stage ambient spring cavity of body during freezing conditions (such as where surrounding water temperature is 50 degrees Fahrenheit or 10 degrees Celsius, or lower), the adiabatic condition will super cool the regulator first stage to the point where ice forms on the internally located first stage spring. As ice formation increases, a solid bridge of ice will form between the spring coils. As the ice hardens, the coils become linked together and solid ice prevents the spring form compressing or deflecting.
What is needed therefore is a way to prevent water from entering and forming ice between the coils of the intermediate pressure spring or inside the ambient pressure cavity.